This section provides background information relates to the present disclosure and is not necessarily prior art.
Some vehicles include passive entry systems that allow a user to unlock the vehicle from a key fob that is located a distance away from the vehicle. The vehicle transmits a signal to the key fob located a distance (e.g., 3 meters) away upon a vehicle triggering event (e.g., touching a handle of the vehicle, pulling the handle of the vehicle, or pushing a start button of the vehicle). The key fob transmits the signal and the key fob's identification back to the vehicle. If the vehicle recognizes the signal and the key fob's identification as belonging to the vehicle, and the key fob is at an exterior of the vehicle, the vehicle is unlocked. Similarly, if the vehicle recognizes the signal and the key fob's identification as belonging to the vehicle, and the key fob is at an interior of the vehicle, the vehicle is started.
These passive entry systems are susceptible to relay attacks wherein thieves extend the range (e.g., 1 km) of communication between the vehicle and the key fob. One thief is located at the vehicle with one relay attack device to communicate with the vehicle. Another thief is located a distance away from the vehicle with another relay attack device to communicate with the key fob. The one thief performs the vehicle triggering event and intercepts the signal transmitted from the vehicle using the one relay attack device. The one relay attack device transmits the intercepted signal to the other relay attack device, which transmits the intercepted signal to the key fob. The key fob receiving the intercepted signal from the other relay attack device transmits the signal and the key fob's identification back to the vehicle, thereby causing the vehicle to unlock or start. The teachings of the present disclosure provide a passive entry system that prevents thieves from using the signal transmitted from the vehicle to unlock or start the vehicle.